摘要:

Using comparative techniques to account for phylogenetic effects, I examined patterns of evolution of caudal autotomy and foraging in 39 lizard species to test the hypothesis that caudal autotomy has co‐evolved with morphology, locomotor performance, and foraging behaviour. There were significant positive associations between evolution of the point on the tail (distance from cloaca) at which tail loss occurs (an indirect measure of caudal autotomy) and evolution of each of the following: tail length,caudifemoralis longus(CFL) muscle length, and jump distance. The correlation with the evolution of sprint speed approached significance. These relationships primarily were due to the influence of tail‐length evolution on autotomy‐point evolution. With the effect of tail‐length evolution removed, autotomy‐point evolution was negatively correlated with the evolution of tail‐loss frequency. The CFL restricts tail loss to portions of the tail posterior to the most distal point of its insertion in the tail. In addition, with the effect of tail‐length evolution removed, CFL length co‐evolved with sprint speed. These results indicate that tail morphology has co‐evolved with caudal autotomy such that the evolution of the CFL has reduced caudal autotomy in certain groups of lizards.Ambush foraging, the ability to lose the tail, intermediate CFL length, and low locomotor performance (i.e. slow sprint speed and short jump distance) are hypothesized to be the ancestral conditions in lizards using outgroup rooting. The diversification of lizard taxa has resulted in some lineages moving away from ancestral character states (i.e. family Teiidae, superfamily Varanoidea), while others are very similar or identical to their ancestors (i.e. sup

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05280.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Cryptomys darlingiis a social subterranean rodent mole which inhabits the mesic regions of south‐eastern and central Africa. Mashona mole‐rats live in small colonies (5‐9 animals) in which reproduction is normally restricted to the largest male and female in the colony. The non‐reproductive members in a mature colony cannot be placed into clearly defined work‐related groups based on body mass.The dominance hierarchy of a young colony was found to be linear, with a value of 1.00 calculated from Landau's linearity index, while that of a mature colony of nine mole‐rats was almost linear (0.77). Dominance was found to be related to gender in the mature colony, with males more dominant than females, and to age in the young colony. The reproductive mole‐rats are the dominant animals within their respective genders. Dominance appears to correlate positively with body mass (rs = 0.77 in the mature colony and rs = 0.93 in the young colony).Popularity studies show that smaller animals and females tend to be more popular than the larger massed individuals or males. In the mature colony which contained predominantly adult animals, the reproductive pair was among the least popular. While in the young colony, composed predominantly of sub‐adult and juvenile animals, the reproductive pair was the most popular.Social organization within Mashona mole‐rat colonies is compared with other southern Africa

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05281.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Reproduction in round‐eared elephant shrews occurred throughout the year. Male round‐eared elephant shrews were spermatogenically active, with spermatozoa stored in the cauda epididymes, throughout the year. Pregnant females occurred in all months except March and May and there was a decline in the occurrence of pregnancies during early winter (March‐July). This tendency towards seasonality of pregnancies was mirrored by the appearance of juveniles, with 77% of all young animals caught between September and February. Bone calcium concentrations were significantly lower during the dry winter than during summer. From October onwards (the beginning of the wet season), bone calcium concentrations increased, reaching high levels in December which were maintained until April. This increase in bone calcium concentrations coincided with the rainy season and with an increase in the intake of herbage, and during this period 60% of all pregnancies occurred. We conclude that the ability of the round‐eared elephant shrew to vary its diet may allow some individuals to breed throughout the year. The reduction in the occurrence of pregnancies in early winter probably ensures that few births occur when bone calcium concentrations

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05282.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The ophiuroid arm contains a series of vertebral ossicles that form an articulated internal skeleton. Ontogenetic, serial, and interspecific variation in these skeletal elements are investigated using morphometric data from 35 species of brittle‐stars (Order Ophiurae). Multiple ossicles were sampled from each individual and several individuals were sampled from each species to reconstruct serial and ontogenetic changes in vertebral morphology. Within species, ontogenetic and serial allometries are not statistically different. These data support ‘Jackson's law of localized stages’ (Jackson, 1899; Clark, 1914), which proposes that serial variation along the arm reflects ontogenetic stages of ossicle growth.A multivariate analysis of interspecific variation shows two major vertebral forms: ossicles with a proximal depression and distal keel, and ossicles lacking these features. Variation within these groups is largely continuous, but individual species show distinct shape differences and unique allometric patterns of serial variation. These results suggest that vertebral ossicle variation among species can be described by: 1) variation in initial shape; and 2) variation in the allometric trajectory along the proximal‐distal axis.In all species, the most proximal ossicles within the disk show a non‐keeled morphology. In species with keeled arm ossicles, however, there is an abrupt transition within the disk between non‐keeled and keeled vertebral forms. A single ossicle, having features of both vertebral types, occurs at this site. The taxonomic distribution of the two vertebral forms and the anatomical transition between forms is discussed with reference to current classification systems and recent phylogenetic schemes for the

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05283.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Analysis of 105 scats of the maned wolf (Chrysocyon brachyurus) collected in central Brazil yielded 304 occurrences of food items of which fruits ofSolanum lycocarpum, rodents, and birds accounted for 61.5%. By analysis of minimum number of individual animals, rodents and birds were 75% of a total of 156 prey. On the other hand, fruits ofS. lycocarpumand armadillos (Dasypusspp.) were the bulk of the total estimated biomass consumption, yielding 63.7% in a total of 73.5 kg. Rodents were mostly captured during the dry season, while miscellaneous fruits were consumed mostly in the wet season. The consumption ofS. lycocarpumfruits and armadillos was aseasonal. Small rodents were taken in about the ranks of abundance in the study area, butS. lycocarpumfruits were actively searched by maned wolves, for its occurrence is limited to secondary savanna. Prey and fruits typical of savanna (‘cerrado’) and grassland (‘campo’) were the bulk of species, occurrences, prey numbers, and biomass consumed. These findings reinforce the importance of conservation of cerrado and campo in central Brazil. Despite maned wolf being a vulnerable species, its feeding habits are opportunistic, and the main reasons for its decline are likely to be habitat destruction and human dist

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05284.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Population densities of red and roe deer were estimated in 20 conifer plantations throughout central and northern Scotland. Ten forests were selected on the basis of culling records that were considered likely to cover the range of possible densities. Ten further forests were selected at random to investigate the relationship between red and roe deer densities. Density assessment was by standing‐crop dung‐group counts, on 1.5 x 100 m transects. Dung decay rates were estimated in four areas and used to convert the values to deer densities. Red deer densities were estimated to range from 0.3‐35 km−2; roe deer densities ranged from 0.5‐25 km−2. Preferences for different structural habitats within individual forests (i.e. blocks with different age classes of tree) were inferred from dung densities. Red deer preferred unplanted ground, open‐thicket, and prethicket; roe deer likewise preferred prethicket (highly) and open‐thicket. Both species avoided closed‐canopy habitats. Red and roe deer densities were negatively correlated and the relationship was significant when the data were log tra

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05285.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Males of the midgeChironomus plumosusfly solely to mate. They maintain station for long periods in moving air. Females patrol in search of males and, after receiving a spermatophore, fly to oviposition sites. The requirements of flight in males and females are therefore fundamentally different. Females are larger than males, on average, so these differences could stem from scaling rules governing the geometry of space. The same explanation might apply to flight differences within the sexes and even to peculiarities of flight architecture inC. plumosuscompared to other flying animals. In other words, might flight design be accounted for entirely by mechanical constraints without recourse to natural selection?To test this hypothesis, the power output ofC. plumosuwas measured as size‐specific muscle mass. Contrary to expectation, little evidence was found of scaling effects in this measure of power. Despite its being among the smallest of animals to fly,C. plumosusturns out to have the largest mass of flight muscle, relative to body size, yet found among animals. Differences both betweenC. plumosusand other species and withinC. plumosusare, in general, more readily accounted for by the requirements of the mating system within the viscous universe encountered by small flying animals. We conclude that it is natural selection rather than mechanical constraint that is the primary influence determining the architecture of flight in this small anima

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05286.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Rate of metabolism, body temperature, wet thermal conductance, and evaporative water loss were measured at different ambient temperatures in four lesser gymnuresHylomys suillus.Gymnures responded as typical endothermic homoiotherms to changes in ambient temperature. Below the lower critical temperature of 32°C, they maintained a body temperature of 37.3± 0.3°C by an increased rate of metabolism. Minimum wet thermal conductance was 111% of that expected on the basis of body mass. Average basal rate of metabolism was 1.04 ml O2g−1h−1, which represents 106% of the expected value. Within and above the thermoneutral zone, heat loss by evaporation did not account for more than 30% of the heat produced. As a consequence, the body temperature of gymnures was maintained 4°C above ambient temperature. These metabolic and thermoregulatory patterns differ strikingly from those of other members of the family Erinaceidac and can be interpreted as a result of physiological adaptation to a different ecology. Being smaller than hedgehogs and inhabiting montane tropical rainforests, lesser gymnures lack the physiological traits which enable many hedgehogs to invade hot, arid and/or strongly seasonal envir

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05287.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The beaver, exterminated in Sweden in the 19th century, was reintroduced in the 1920s. The population is still increasing its range and individuals at the expansion front can still move into optimal habitats. Therefore, there is no need for beavers to occupy marginal habitats, and preferred habitats are not yet altered by the beavers themselves. Salient features of occupied and unoccupied habitats were analysed by partial least square projections to latent structures (PLS) in order to identify the important factors. The tortuosity of streams, and occurrence of grasses and forbs in the ground layer, had the strongest positive effects. Availability of deciduous forest differed univariately between used and unused sites, but added little to the model. It is suggested that variables describing geomorphological stages in stream development will increase both the general applicability and reliability of studies that attempt to assess the quality of beaver habitat.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05288.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The ecology and general biology of African snakes remains virtually unstudied, even in highly distinctive species such as the filesnakes (generaMehelyaandGonionotophis). Our measurements and dissections of preserved specimens provided information on body sizes, sexual dimorphism in size and bodily proportions, clutch sizes, and food habits of twoMehelyaspecies. In bothM. capensisandM. nyassae, females attain sexual maturity at the same size as conspecific males, but grow to much larger sizes.Mehelya capensisdisplays extreme differences in body shape between males and females at the same body length: females have longer and wider heads, thicker bodies, and larger eyes (relative to both head length and head width) than do conspecific males. Dimorphism in body proportions is less marked inM. nyassae.Female reproductive cycles are seasonal inM. capensis, and clutch sizes are larger in this species than in its smaller congener (5‐11 eggs inM. capensis, 2‐6 eggs inM. nyassae).Contrary to popular wisdom,Mehelyaare not specialized ophiophages.Mehelya nyassaefeeds primarily upon lygosomatine skinks, including many fossorial taxa.Mehelya capensishas a broader diet, feeding on a wide variety of terrestrial lizards (especially agamids and gerrhosaurids) and snakes. Toads are also common prey items. The diversity of prey types taken byM. capensissuggests that these snakes may use ambush predation as well as active foraging.Mehelyais strongly convergent with Asian elapids of the genusBungarusin its morphology (triangular body shape; powerful jaws; visible interstitial skin), behaviour (nocturnality; reluctance to bite when harassed), and diet (feeding on elongate reptiles, including snakes). Observations of preyhandling and ingestion by captive snakes are needed to clarify possible selective forces for the evolution of the unusual traits shared by these t

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05289.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY